We study the formation of molecular precursors to dust in the ejecta of Population III supernovae using a chemical kinetic approach. Our work focuses on zero-metallicity 20 Msun and 170 Msun progenitors, and we consider fully-macroscopically mixed and unmixed ejecta. The nucleation stage for small silica, metal oxides and sulphides, pure metal, and carbon clusters is described with a new chemical reaction network. We consider the effect of the pressure dependence of critical nucleation rates, and test the impact of microscopically-mixed He+ on carbon dust formation. The unmixed ejecta of a 170 Msun progenitor supernova synthesizes ~ 5.6 Msun of small clusters, while its 20 Msun counterpart produces ~ 0.103 Msun. Our results point to smaller amounts of dust formed in the ejecta of Pop. III supernovae by a factor ~ 5 compared to values derived by previous studies, and to different dust chemical composition. Such deviations result from some erroneous assumptions made, the inappropriate use of classical nucleation theory to model dust formation, and the omission of the synthethis of molecules in supernova ejecta. Unmixed ejecta of massive Pop. III supernovae chiefly form silica and/or silicates, and pure silicon grains whereas their lower mass counterparts form a dust mixture dominated by silica and/or silicates, pure silicon and iron sulphides. Amorphous carbon can only condense in ejecta where the carbon-rich zone is deprived of He+. The first dust enrichment to the primordial gas in the early universe from Pop. III massive supernova comprises primarily pure silicon, silica and silicates. If carbon dust is present at redshift z> 6, alternative dust sources must be considered.
We investigated continuum and molecular line emission of four species (CO, HCN, H$^{13}$CN, and HCO$^+$) at 0.8 mm in the inner arcsec around Eta Car, using ALMA archival observations at a resolution better than 0.2 arcsec. We report the discovery of an asymmetric extended structure northwest of the star, independent from the continuum point source. The structure is only traced by continuum and HCO$^+$, and not detected in the other lines. Kinematics of this structure reveal that the HCO$^+$ gas likely arises from ejecta expelled in the 1890s eruption. The ejecta is propagating outward within …
The central star of the planetary nebula (PN) HuBi\,1 has been recently proposed to have experienced a very late thermal pulse (VLTP), but the dilution of the emission of the recent ejecta by that of the surrounding H-rich old outer shell has so far hindered confirming its suspected H-poor nature. We present here an analysis of the optical properties of the ejecta in the innermost regions of HuBi\,1 using MEGARA high-dispersion integral field and OSIRIS intermediate-dispersion long-slit spectroscopic observations obtained with the 10.4m Gran Telescopio de Canarias. The unprecedented tomographi…
We model dust formation in the core collapse supernova explosion SN 1987A by treating the gas-phase formation of dust grain nuclei as a chemical process. To compute the synthesis of fourteen species of grains we integrate a non-equilibrium network of nucleating and related chemical reactions and follow the growth of the nuclei into grains via accretion and coagulation. The effects of the radioactive cobalt, titanium, and sodium on the thermodynamics and chemistry of the ejecta are taken into account. The grain temperature, which we allow to differ from the gas temperature, affects the surface-…
The formation of bimodal dust species (namely the silicate and amorphous carbon dust grains coexistent) in a nova eruption is an open problem. According to the nova model simulated by Modules for Experiments in Stellar Astrophysics code, we calculate the formation and growth of carbon (C) and forsterite (Mg2SiO4) dust grains purely in nova ejecta for the fee-expansion model and the radiative shock model by assuming spherical geometry of the nova ejecta. In these models, the chemical properties of pre-existing circumstellar medium are not taken into account. In the free-expansion model, the nov…
Revisiting the formation of molecules and dust in core collapse supernovae
Université de Montpellier, CNRS（蒙彼利埃大学，法国国家科学研究中心）；Consejo Superior de Investigaciones Cientificas, Instituto de Fisica Fundamental（西班牙高等科学研究理事会，基础物理研究所）
Discovery of sulfur oxides in the ejecta of a B[e] supergiant
INAF – Osservatorio Astrofisico di Catania（意大利国家天体物理研究所卡塔尼亚天文台）；Instituto de Astrofísica de Andalucía (IAA-CSIC)（安达卢西亚天体物理学研究所（西班牙高等科学研究理事会））；ISDEFE（空间系统与地球观测技术研究所）；Centro de Astrobiología, CSIC-INTA（天体生物学中心（西班牙高等科学研究理事会-国家航空航天技术研究所））；Joint ALMA Observatory（ALMA联合 observatory）
An observational study of dust nucleation in Mira ($o$ Ceti): II. Titanium oxides are negligible for nucleation at high temperatures
演化恒星富氧包层中硅酸盐尘埃的形成被认为是由种子粒子的形成引发的，种子粒子可以承受恒星光球层附近的高温，并在远离恒星的地方充当凝结核。被认为是第一缩合物的候选物种是TiO和TiO $_2$。我们的目标是确定和表征的钛的拱星气相化学，导致形成固体钛化合物的信封中的$o$ Cet，原型米拉，并寻求一个观察验证钛氧化物是否发挥了主要作用的尘埃形成的M型AGB星的发病。我们提出了高角分辨率ALMA观测亚毫米（submm）波长补充的APEX和赫歇尔光谱的旋转功能的TiO和TiO $_2$。此外，在覆盖$o$ Cet的多个脉动周期的光谱中，确定了TiO和TiI的星周特征。亚毫米ALMA数据揭示了在扩展的米拉大气中含有TiO和TiO $_2$的气体。虽然TiO可追踪到4.0 R $_{\star}$的半径（FWHM/2），但TiO $_2$延伸远至5.5 R $_{\star}$，并且与TiO不同，TiO似乎是各向异性分布的。光谱显示TiI和TiO从扩展大气（<3 R $_{\star}$）内部的可变发射。包括冲击的化学模型与气相含钛分子的观测结果基本一致。由于气态钛物质的丰度非常高，因此不太可能将大量的钛锁定在固体中。特别是，热的富钛冷凝物的形成是非常不可能的，因为我们发现在气相中没有热的前体物质的痕迹。因此，Mira和其他M型AGB星的尘埃不太可能是由氧化钛引发的。
Heavy element dust explains the late-time spectra of kilonovae
The University of Tokyo（东京大学）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
Supernova (SN) 1987A is the only young SN in which H_2 has been detected in the ejecta. The properties of the H_2 are important for understanding the explosion and the ejecta chemistry. Here, we present new VLT/SINFONI observations of H_2 in SN 1987A, focussing on the 2.12 μm (1,0)S(1) line. We find that the 3D emissivity is dominated by a single clump in the southern ejecta, with weaker emission being present in the north along the plane of the circumstellar ring. The lowest observed velocities are in the range 400-800 km/s, in agreement with previous limits on inward mixing of H. The brighte…
AGB stars are, together with supernovae, the main contributors of stellar dust to the interstellar medium (ISM). Dust grains formed by AGB stars are thought to be large. However, as dust nucleation and growth within their outflows are still not understood, the dust-grain size distribution (GSD) is unknown. This is an important uncertainty regarding our knowledge of the chemical and physical history of interstellar dust, as AGB dust forms $\sim$ 70% of the starting point of its evolution. We expand on our chemical kinetics model, which uniquely includes a comprehensive dust-gas chemistry. The G…
Classical novae commonly show evidence of rapid dust formation within months of the outburst. However, it is unclear how molecules and grains are able to condense within the ejecta, given the potentially harsh environment created by ionizing radiation from the white dwarf. Motivated by the evidence for powerful radiative shocks within nova outflows, we propose that dust formation occurs within the cool, dense shell behind these shocks. We incorporate a simple molecular chemistry network and classical nucleation theory with a model for the thermodynamic evolution of the post-shock gas, in order…
Aluminum oxide (alumina, Al$_{2}$O$_{3}$) is a promising candidate as a primary dust condensate in the atmospheres of oxygen-rich evolved stars. Therefore, alumina \textit{seed} particles might trigger the onset of stellar dust formation and of stellar mass loss in the wind. However, the formation of alumina dust grains is not well understood.} {To shed light on the initial steps of cosmic dust formation (i.e. nucleation) in oxygen-rich environments by a quantum-chemical bottom-up approach.} {Starting with an elemental gas-phase composition, we construct a detailed chemical-kinetic network des…
Astronomical observations and analysis of stardust isolated from meteorites have revealed a highly diverse interstellar and circumstellar grain inventory, including a wide range of amorphous materials and crystalline compounds (silicates and carbon). This diversity reflects the wide range of stellar sources injecting solids into the interstellar medium each with its own physical characteristics such as density, temperature and elemental composition and highlights the importance of kinetics rather than thermodynamics in the formation of these compounds. Based upon the extensive literature on so…
